Baculoviruses are important as biological insecticides and are of interest from a basic virological perspective because of their large circular, double-stranded, supercoiled DNA genomes, their extendable rod-shaped nucleocapsids and their complex developmental cycle involving the production of two distinct types of virus particles--an occluded and a non-occluded form. Our research explores the molecular biology and genetics of baculoviruses with particular emphasis on the model system Autographa californica nuclear polyhedrosis virus (AcNPV). We propose to construct a functional map of AcNPV which would detail the positions of a reasonable proportion of early, middle and late virus-specific proteins. Information concerning the locations and temporal patterns of AcNPV gene transcription will be obtained. The possibility of gene splicing of some AcNPV transcripts will be explored. Site-specific mutagenesis including the insertion and expression of the E. coli beta-galactosidase gene in AcNPV will be undertaken. This latter work is focused primarily on the role of various proteins in the viral occlusion process and should allow further exploration of the control of gene transcription during virus development. A major portion of the work will also explore the movement and expression of transposable elements inserted in the AcNPV genome. We first will explore the nature of a copia-like transposable element which has inserted itself into the AcNPV DNA genome and exhibits a novel genetic instability. By determining the structure of the element, analyzing its expression, exploring the mechanism of transposition, and assessing the effects of the element on the expression of surrounding viral genes, a more comprehensive understanding of transposition in eukaryotes will be obtained. The impact of transposable elements on baculovirus genetics will be explored and the possibilities of P-element insertion and transposon mutagenesis of AcNPV will be explored. The research should be of fundamental genetic and virological interest and will be essential to our assessment of the safety of these viruses as pesticides.